Question

The degree of dissociation of a $0.01M$ weak acid is $10^{-3}$ . Its $pOH$ is

• A. $5$
• B. $3$
• C. $9$
• D. $11$

Answer 1

Answer: (C)

$\left[H^{+}\right]=\sqrt{K_a\cdot C}$

or $=\sqrt{{\alpha }^2\cdot C^2}$

$\left[\therefore K_a={\alpha }^{2}C\right]$

$=\sqrt{{\left(10^{-3}\right)}^2\cdot (0.01{)}^2}$

$=10^{-5}$

$pH=-\log \left[H^{+}\right]=-\log 10^{-5}$

$=5$

$pOH=14-5=9$